Single-use disposable liquid packages are manufactured of flexible laminated packaging material and are used for a plurality of various products, for example milk and juice. Normally, the packaging laminate essentially comprises a central carrier layer of fibrous material, for example paper, which is coated on either face with liquid-tight layers of thermoplastic, primarily polyethylene. When the package is intended for filling with previously sterilized contents, for example UHT treated milk, the packaging material normally also includes a barrier layer of, for example, aluminum foil, which is disposed at the surface of the packaging material facing the interior of the package and is covered with an additional layer of thermoplastic material, preferably polyethylene.
Packages which have been formed by folding and heat-sealing of the laminate often include some form of prepared opening arrangement, for example a line of weakness which defines a tear-off portion of the wall of the package. To facilitate tear-off, the tearable wall portion is often provided with a projecting gripping device by means of which the consumer may open the package. The package may also be provided with handles or other exteriorly applied plastic details.
In the manufacture of packages of the aseptic type, i.e. packages which are intended to be filled with previously sterilized contents, it is of crucial importance that the package be not only liquid-tight, but also gas-tight. Since the packaging material is normally sterilized by passing it through a bath of liquid chemical sterilization agent, it is also important that the packaging material not include any loose or projecting details, since such details--like areas of untightness--not only entrain a concentrated, large volume of sterilizing agent out of the bath, but also impede the removal of the sterilization agent using conventional means such as squeezer rollers and so-called air knives, in other words hot air curtains. Prefabricated details applicable to the outside of the packaging laminate such as gripping devices and handles cannot, therefore, normally be employed in packages of the above-mentioned type.